The present invention relates to the reconstruction of buried damaged conduits and pipelines, in particular sewers, and more specifically to a liner hose for use in such reconstruction and a method of manufacturing such a liner hose.
In the reconstruction of damaged buried conduits or pipelines such as sewers it has become customary practice to draw a flexible collapsed liner hose comprising at least one layer impregnated with a curable resin through a length of the damaged conduit or pipeline followed by internal expansion of the liner to a desired tubular form matching the walls of the conduit or pipeline and exposing the interior of the liner hose to a curing agent, typically hot water or steam, which is introduced into the hose length to fill it from one end to the other and retained in the hose for a curing period of a duration sufficient to expand the hose to contact the walls of the conduit or pipeline and cure the resin. Alternatively, curing may be effected after expansion of the collapsed hose to form a tubular liner by exposure of the liner to ultraviolet radiation.
Thereby a solid and rigid lining, which is also resistant to the typically aggressive fluid matter carried through the conduit or pipeline, is established inside the damaged conduit or pipeline and complete renewal of the conduit or pipeline itself and the extensive expenses in connection therewith are avoided.
Numerous examples of liner hoses for such conduit reconstruction have been disclosed or suggested in the prior art.
In traditional liner hoses a single layer or overlapping layers of impregnated material, typically felt, fleece or other impregnatable material are confined between inner and outer layers of water-tight plastic film and formed into a hose by joining opposed longitudinal edges of the layer structure into a seam by welding or other appropriate methods. Such hoses have generally suffered from the disadvantage that they only fit one specific conduit or pipeline diameter.
Liner hoses of this traditional type have been disclosed e.g. in GB patent No 1,340,068.
In most cases, the damaged conduit or pipeline to be reconstructed will exhibit more or less significant local irregularities from the ideal circular cross-sectional profile and, if no countermeasures are taken, such irregularities may result in formation of an annular clearance between the external side of the liner hose and the walls of the conduit or pipeline with a resulting risk of penetration of water from the outside into such clearances.
In order to adapt liners hoses to provide a tight engagement with the wall of the conduit or pipeline some prior art solutions, e.g. as disclosed in European Patent Application No. 0 863 359, have prescribed the use of fibrous layers having significant elastic stretchability in the circumferential direction, up to 15 percent.
Such a stretchability results in the disadvantage, however, that uncontrollable variation in the wall thickness of the liner hose may occur. In order to counteract this disadvantage, it is suggested in the European Patent Application quoted above to use intermediate layers which overlap each other and are firmly bonded together in the overlap sections.
Other prior art solutions such as disclosed in German Patent Application No. 41 13 002 and German Patent No. 44 27 663, have suggested the use of overlapping intermediate layers which are not bonded together in the overlap sections, so that a certain stretching of the hose structure in the circumferential direction is made possible through displacement of such overlapping layers with respect to each other. In general, it has been prescribed for such solutions that the overlap sections must be uniformly distributed throughout the circumferential length of the liner profile.
Thereby, the individual fibrous layers may be prepared substantially without circumferential stretchability from fibres orientated mainly in the circumferential or transverse direction resulting in a very high circumferential rigidity of the liner after curing of the resin. In the attempts to reach a maximum of circumferential rigidity it has been disregarded, however, that by use of a general fibre orientation in the circumferential direction longitudinal stretchability of the liner hose may result, whereby local stretching may occur, when a liner hose of significant length is drawn through a damaged conduit or pipeline.
Moreover, all the prior art solutions in respect of using overlapping intermediate layers, whether bonded of unbonded in the overlap sections, have suffered from the disadvantage of a rather complicated manufacturing process requiring a separate folding step for each intermediate layer and a complicated impregnation process.